Neutron Optical Studies of Fundamental Phenomena of Quantum Mechanics

Neutron interferometric and polarimetric experiments serve as almost ideal tools to investigate foundation of quantum mechanics with matter waves. For instance, while the former device is used for studies of characteristics of intra-partite entanglement, i.e., entanglements between degrees of freedom, the latter is used for studies of anti-commuting properties of Pauli spin matrices and topological phase measurements. Exploiting both strategies, alternative theories of quantum mechanics are tested: violations of Bell’s inequality for bi-partite entangled states as well as inequality derived by Mermin applied for tri-partite entangled states are demonstrated. Moreover, Kochen-Specker theorem and a crypto-contextual model suggested by Leggett are studied. Furthermore, the uncertainty relation is studied with neutrons experimentally: recent rigorous and general theoretical treatments of quantum measurements suggest the failure of Heisenberg’s original relation between the error and the disturbance of the measurements. We have tested the error-disturbance uncertainty relation in neutron’s spin measurements. Experimental results demonstrate the violation of the Heisenberg’s original relation and confirm the validity of the new relation. In addition, I am going to explain a new counter-intuitive phenomenon, called quantum Cheshire-Cats, observed in a neutron interferometer experiment.